1. Technical Field
The present invention relates to a start control unit for a steam turbine plant.
2. Background Art
In recent years, to preserve fossil resources, power generation facilities using renewable energy such as wind power and sunlight are increasing. However, the power generation quantity from these kinds of renewable energy varies greatly depending on the weather and season. To promptly supplement such variations in the power quantity and stabilize the power system, power generation facilities such as a combined cycle power generation plant and a coal burning power generation plant are required to start in a short period of time. One of the methods of starting the power generation plant in a short period of time is to quicken the start of the steam turbine which is a component of the power generation plant (hereinafter referred to as high-speed start).
The steam turbine includes a rotor which is a rotating body and a casing for surrounding the rotor as components. Upon starting the steam turbine, high-temperature steam is fed, the casing and rotor are heated by the heat of the high-temperature steam, and elongation is generated in both the casing and the rotor due to the thermal expansion (this elongation is hereinafter referred to as thermal elongation). Here, generally, due to the causes such that the casing is higher in the thermal capacity than the rotor and that the casing discharges heat into the atmosphere via an insulation material, the casing has a tendency to become delayed in the thermal elongation at the time of start than the rotor. As a result, if the thermal elongation difference becomes excessive, there is a possibility that the casing which is a stationary portion and the rotor which is a rotating portion will come into contact with each other, which can cause a reduction in the reliability or performance of the device.
As a countermeasure for it, conventionally, a method is proposed of reducing the thermal elongation difference between the casing and the rotor by estimating the thermal elongation difference generated by the steam turbine between the casing and the rotor and then controlling the steam flow rate so that the estimated value will be suppressed to the regulated value or smaller (for example, Patent Literature 1).